Loud-speaker arrangement



June 11, l

H. BENECkE 2,203,715

LOUD-SPEAKER ARRANGEMENT Filed Feb. 10, 1937 2 Sheets-Sheet l F592 6 "fi Q Q ,Q

lnvenzor:

V w gM/ u A TTOR/VE) June 11, 1940. H, BENECK; 2,203,715

LOUD-SPEAKER ARRANGEMENT Filed Feb. 10, 1937 2 SheetsSheet 2 Inventor:

HE/IVR/Ch' awn/ 5 4 T TOR/VF Y Patented June 11, 19 40 Telefunken Gesellschaft fiir Drahtlose Telegraphic, in. b. 11., Berlin, Germany, a corporation of Germany Application February 10, 1937, Serial No. 124,998 In- Germany February 17, 1936 1 Claim. 7 (Cl. 181-1-05) V H V duced in the manner that a loud-speaker sys- In the directed radiation of sound the fact is felt in disturbing manner that the surfaces efiecting the directional action are operative only so long as the wavelength is not essentially larger than the linear dimension of the system. If for one reason or another (obstruction of vision) conical and similar guiding surfaces of large dimensions cannot be used, the low frequencies spread unhindered and undirected-and cause in many cases, in particular if the ground to be covered is large, disturbances, in particular the doubling of speech. Another great fault is the impossibility to direct low frequencies towards the ground in such a way that they are absorbed 1 beyond even a short distance as in the casefor medium and high frequencies with systems of average dimensions. I

The invention is concerned withthe decrease of too large a range for loud-speakers; particularly of the low frequencies; in other words the sound waves radiated by the loud-speaker should practically be audible for a certain distance only. v k This may be accomplished in various manner. 'l'he range of the sound waves is limited in ac 26 ccrdance with the invention in especially suitable manner by causing the intentional production of strong interferences in a sound field produced by aloud-speaker. a This may, for instance, be accomplished in the 30 manner that with a loud-speaker. diaphragm whose radiations are equal on both sides and where with excitation on the one side of the dia hragm the air is compressed, and on the other side rarefied or thinned out, there appear in the 35 plane at right angle to the direction of axis of the diaphragm zones wherein the sound waves are extinguished. The range of extinctionincreases with increasing distance-from the sound source. There are produced in thismanner sep- 40 arated by zones of extinction, substantially conelike regions wherein the sound waves are perceptible. The axes of the regions wherein the sound waves are perceptible, are' disposed substantially in the direction of diaphragm axis.

4 to the space or area which is to be covered by the speech in such manner that the axis of the conical region wherein the sound waves are perceptible, is preferably at right angles to the sur- 50 face to be covered. In this manner a region is in ured around the sound source wherein the soundwaves are perceptible and which is surrounded shell-like by. a zone of extinction and whose. range is thus small relatively with respect 55 to the range of sound waves ordinarily in use. Above the diaphragm a further conical region exists wherein sound waves are likewise perceptible. jHowever, this region cannot usually be utilized for the transmission.

50 Such a sound field may for instance be pro- The diaphragm now is orientated with respect L curs inthe same instant. .one or several systems shall be designated hereinafter as a tem is used with a singlediaphragm But also several diaphragms may be provided, each of which is preferably driven s'eparately.and arranged in the manner that the one loud-speaker radiates in the one direction; the otherloudspeaker in the opposite direction.

Care must be taken in all these constructions that a substantially equal sound field is produced on both sides of the diaphragm. Particular' attention. must be paid to th s point with the use of a driving system with one diaphragm alone since the system must be throughout developed in the manner that the above mentioned demand regarding the sound field is met. If on stantially downward, whilethe diaphragm of the other system radiates upward. The directions of the axes of the diaphr'a'gms coincide. The two systems are installed in an acoustically closed space. The diaphragms' form part of 'the walls of this space. The one side of each diaphragm acts upon the outer air and in such manner that the diaphragms vibrate in counterrhythm, with respect to the outer soundfield. In other words,

if these two systems are considered as a joint unit, theair is attenuated at the front side in front of one diaphragm and densified in front of the other diaphragm. Hence, from an elec trical standp int the diaphragms operate in phase opposition. Howevenfrom' an acoustical. point of view they operate in like phase, thatis, in the same sense. A further requirement consists in that the diaphragms vibrate synchronously and with equal amplitudes. Accordingly, if. one diaphragm moves away from the system, the other diaphragm moves towar the system. The reversal of both diaphragm mo ements oc- Such a structure with v pushpull twin radiator.

Exemplified embodiments of loud-speakerarrangements in accordance with the invention are disclosed in the appended drawings wherein Fig. 1

1 discloses a pair,of loud-speaker imits arranged to .produce a horizontal zoneof extinction in accordance with the invention, Fig. 2 is an explanatory diagram in'conne'ction with 1, Fig. 7 is a modification of Fig., 1 wherein the sound from a pair of loud speaker units is re.- diated in the same direction, and Figs. 4 to 7 illustrate various modes of operation of a pair of loud-speaker units such as disclosed in'Flg. 1.

- the other hand two systems are chosen, the usual without making felt in distm-bi ngg hand. the high frequencies spread asymmetricmanner.'Butin-theillsh-pulltwin allya V -radiator-the central horisontal plane I has the Pigs.4 to? illustrateinschematicmannereb. ll distinction that all'frequencies are v ed; emplifled cuts for operation of 16' Thisextinctionexistseven'wlthinatwin" torserebythemembranesotthe certainangular'rangearwndthisplaneandthe 'loudertdonotexactlyvibrate dk tan'ce o f the suitable as close-action loud-speaher, particular bank :6;- which it-has its rflem thlls for r w 100!) cycles. Thai-above -sthese are then to be-radiatcd by mam.

. i l m radiator we her that does notexceed o thatoithepush-pull-twinladlator.

q; where he soirndradiated by j 59 The practical application ofthe push-pull indi '2' aaosms at. ishowstwo loud-o l, 2 3r telnselnergesinonedirectiononlm-lioud-speaker theusual-dimensionslocatedatacertaindistance systems it d II-are enclosed in a pipe-like i'romeach other in a pinenr housing 3 and whose vibrate. looking from the outside, aynchronmlsly as by the arrows. Tiie ,arl'angememis suitably attached to a mast I. Two vibrating at diil'erentpoints must result everywhere in the sound ihald in interierendea Such 'interterences'appear as such everywhere, fol-instance also in'the propagationot;sound in a clocedech'amber housing. Infrontotloud-speakerli and 32 are further arranged. sound guidesit. 3 81! r. 11- www or conical form, have 3| arrangedinthe same direction; Jihe loud-speaker arrangement is attached to a This arrangement insures a propagation of the low frequencies on all sides. is restricted due' to interferen 0n the other in opposite rhythm so that zones oi extinction obtained deviating from the conical shape as cated in Figs. 1 and 2.1111185. 4 to'lthe 90 symbols are chosen for the same elements.

luthecmbodimentaccordingtol igi4,amast' I ll, set on thefground, has attached loud-speaker cred and with vertical axia'that is so that one 'arrang eat 62.. The loud-speaker arrang loud-sheakerwradiates downward, the other upconsists or a pipe-like h ard. 'Thejaudience -w-n in the vicinity of are placed 1 -spea kem ll and 45. Housing 48 loud-speaker at-the-rfoot ot fire system, are is edinthe manner that it may 1 then located sumciently iar away'from the centhe lengthened or shorten Thus is provided 1 tralplaneot-thepush-pulltwmradiatorinordgri anfeasy way to adjust the distance between the to receive anundisturbed aoundileld. 'lhe Iarloud-speakers. The region of extinction starts 80 theris from the foot pointm the 'betweeh the two loud-speakers and and its -s'ystein.thenearerhetotherangeotex+ tlnction aroundthecentml plane This, is shown in schematic manner in'l'lg. 2. ligudspeaker t 6 k attached to'amast which'in onthesrqund.

' As explained before. the eitinctioh-is particularly eifectivelwlth low l qllehcles, in fact with a mutual'distance oi the 01' Slicentimeters thereresultsinthisarrangementata' greater distance a suilldent'attenuation, up to a about 1000 cycles. The region of extinctionis widened'with lesser distance between theloudspeakers the high and in- -0n the other hand. fl 'extmt of the uhdisturbedhearingranfgedepardsonthemutual in the push-pull,

-radla tor andon its height above the ground to be covered. Thus as .means'is given for conditions prevailing ata particujlar-momenttorycasa' r the radiation is as much both indivldual loud thisconditlonha v Sincethepush-pulltwinradiatorhasprovcd' rangeis thegreater thedower the reproduced Irequency, hence the greater its wavelength.

radlator'is in the manner that the radiators installed at a height, for

nstanc s meters, above the ground to be covwhen housing 4: 1 rotatably attached to mast 85 1 a sound field is obtained as shi'iwn fin Fig. 5. ,This furnishes the meansto avoid excessive sound" intensities at the loot point. e

The rotatable arrangement has the further advantage/that the field may-be adapted to localconditions. An application therefor isf illustrated in-lj'ig. 6. The loud-speaker arrange-' mentisset 155 in an open-air theater, arena or other inclined ground ll, -As'may be seen from the sound field, the arrangement can be adjusted 45 in manner that a particularly favorable adaption togro dconditionsisin'sured.

Fig. represen .a further application of the arrangementaccording to invention. In broadcast or installations, where microphones set up in the vicinity of range a: the-Zone of extinction, thu'selimh noting the 'danger'oi' a Microphone I] isinndicated in lyjtor, medium and low it is to be recommendedtoimpres'sonitonlythefl'equency 'v ;4 am

for a'ircquencyhamd or speaker units mounted coaxii lly Wi h n said housing and faged in o pposite direcltion to each k hwmch with a other. means or ac atingj osaid eud-speaker be mt add units in substantially opposite electrical phase the ma and in substantially like-acoustical; phase whereby there is produced a tan-shaped zone 01' extinction which surrounds the common axis or medwmm #1115 the a J and m tsot ojisingma temofflle per.

3 retsa twin but whose range to ousing. II at whosmendis 35 I a the units-and extends in right angles thereto, 20 

